In recent years, since there has been progress in reducing the thickness of component-mounted boards, and the component-mounted boards bend easily, in a case in which components are mounted on a circuit board using a component mounting machine, the circuit board is prevented from bending by supporting the circuit board from below using back-up pins. In order to satisfy the demand for an increase in mounting density and a reduction in size in recent years, frequently, there is a requirement for a double-sided mounting board in which components are mounted to both surfaces of the circuit board. In a case in which the double-sided mounting board is produced using a component mounting machine, first, components are mounted on one surface of the printed circuit board, and subsequently, the printed circuit board is turned over and re-inserted into the component mounting machine, and components are mounted to the remaining other surface of the printed circuit board.
During the mounting of components on the remaining other surface of the printed circuit board, when a back-up pin supporting the printed circuit board from below makes contact with a previously-attached component of the bottom surface of the printed circuit board, since there is a possibility that the previously-attached component will be damaged or the printed circuit board will be pushed upward, as described in PTL 1 (JP-A-2004-335973), the back-up pins are formed of a soft elastic material such as urethane, and when the tip portion of a pin makes contact with a previously-attached component, the tip portion of the pin elastically deforms to prevent the damaging of the previously-attached component or the pushing up of the printed circuit board. In general, a back-up pin capable of elastic deformation is referred to as a “soft back-up pin”.
In a case in which a double-sided mounting board is produced using soft back-up pins, there is a system in which a pin block in which multiple soft back-up pins are formed integrally in a matrix on a block board is used, and a worker pulls off unnecessary soft back-up pins according to the disposition of the previously-attached components for each type of printed circuit board to be produced. Alternatively, as described in PTL 1, there is a system in which multiple attachment holes are formed in the back-up plate (a pin supporting board) in a matrix, a fitting protrusion portion which fits in the attachment holes is formed on the bottom end of the soft back-up pin, and the worker selects the attachment holes which fit the fitting protrusion portions of the bottom ends of the soft back-up pins according to the disposition of the previously-attached components for each type of printed circuit board to be produced and attaches the soft back-up pins to the back-up plate.
In general, in the component mounting machine, fiducial marks on a circuit board are imaged by a camera, the image thereof is processed to recognize the fiducial marks, and a component mounting position on the circuit board is determined using the position of the fiducial marks as a reference. Therefore, as described in PTL 2 (Japanese Patent No. 4014270), there is a system in which the fiducial position detection technique of the circuit board is applied to the position detection technique of the back-up pin, a fiducial mark is provided on the top end surface of the back-up pin, the fiducial mark of the top end surface of the back-up pin is imaged by a camera, and by processing the image to recognize the fiducial mark, the position of the back-up pin is detected.